Embodiments of inventive concepts disclosed herein relate generally to the field of terrain awareness for aircraft. More particularly, embodiments of the inventive concepts disclosed herein relate to systems and methods that display data or provide audible messages related to cautions and/or warning alerts.
Aircraft pilots rely on situational awareness systems, such as, terrain awareness and warning systems (TAWSs), ground proximity warning systems (GPWSs), weather radar systems, and/or a traffic collision and avoidance system (TCAS), to avoid collisions with hazards, such as terrain, man-made structures, weather, and other aircraft. A TAWS may analyze aircraft sensor data and/or other data to predict whether the path of the aircraft is likely to intersect with hazards, such as terrain and/or man-made structures. For instance, such systems may compare an altitude of the aircraft to elevation of terrain near the aircraft and provide an indication of terrain that has a high enough elevation to be of potential concern to the pilot. The TAWS can provide the aircraft pilot and/or other flight crew members with advance audio and/or visual caution and warning alerts of impending terrain or structural hazards, as well as forward looking capability. A TAWS complying with Technical Standard Order TSO-C151c depicts terrain relative to an aircraft's position such that the pilot is able to estimate the relative bearing to the terrain of interest.
Nuisance alerts are alerts issued by equipment that are not desired. Nuisance alerts from equipment, such as, a TAWS, can be alerts that are improperly issued, are premature, have little relevance to the existing flight path, are less critical than other alerts, or are unnecessary because the pilot is already aware of situation causing the alert. For example, a pilot may fly low enough to terrain and trigger an alert, but may consider the alert a nuisance alert because she or he has complete situational awareness. The TAWS algorithms are objective and based on accurate state-of-the-art sensors, but do not consider the pilot's situational awareness. Nuisance alerts can distract a pilot from other critical tasks, cause a pilot to completely ignore the TAWS alerts, or turn the equipment off.
Conventional TAWS have attempted to decrease the number of nuisance alerts by reducing alerting tolerances and margins or even applying deviations from the required alerting envelopes. This approach has driven many of the caution alerts to simply be preambles to their corresponding warning alerts. With this type of approach, the caution alerts require the same response as warning alerts, especially since some TAWS alerting modes only provide a caution alert, or may be issued too late. In addition, with reduced tolerances and margins, the time required to orally issue a caution alert (e.g., 2 seconds) can be longer than the time between the caution alert and the warning alert if the aircraft continues along the same flight path.